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Highlights: [•] BaTiO3–CoFe2O4 multilayer films were prepared by chemical solution deposition. [•] The strain is relaxed and the grain size is increased with the films thickness. [•] Permittivity and saturation polarization increase with the films thickness. [•] A decrease in saturation magnetization of the thickest film is observed. [•] The effect of the microcracks on the films properties is also investigated. [ABSTRACT FROM AUTHOR]

Abstract The structural, magnetic and ferroelectric properties of the Mn-doped chromites YCr 1- x Mn x O 3 (YCMO) (0.39 ≤ x ≤ 0.73) single crystals have been studied. Powder X-ray diffraction results showed an orthorhombic structure for all the samples. Detailed magnetic studies demonstrated strong ferromagnetic (FM) behavior at low temperatures in all the YCMO crystals, which is found to be due to the FM Cr3+–O2-–Mn3+ magnetic interaction. The multiferroic behavior with magnetoelectric coupling was also observed in YCMO. The electric polarization in YCMO can be attributed to the Jahn-Teller distortion instead of magnetic origin. Highlights • Low temperature ferromagnetism was observed in YCr 1- x Mn x O 3 (0.39 ≤ x ≤ 0.73) crystals. • YCr 1- x Mn x O 3 show multiferroic behavior with strong magnetoelectric coupling. • Electric polarization in YCr 1- x Mn x O 3 are ascribed to the Jahn-Teller effect. [ABSTRACT FROM AUTHOR]

We investigate the structural, magnetic, ferroelectric properties, dielectric response, and scaling behavior of Aurivillius compound Bi 4.25 Gd 0.75 Fe 0.5 Co 0.5 Ti 3 O 15 . The substitution of Gd can effectively enhance the room-temperature ferromagnetic property. The ferromagnetic and ferroelectric Curie temperature can be determined to 370 K and 1088 K, respectively. Four thermally activated dielectric relaxations in the temperature range of 10–1000 K are observed. The first dielectric relaxation in cryogenic temperature range (50–100 K) can be attributed to electron hopping between Co 2+ and Co 3+ through bridging oxygen vacancies V o . The second one in 300–500 K can be ascribed to the electron localized transfer between Co 2+ and Co 3+ . The third one in dielectric anomaly region (500–800 K) arising from the trap-controlled ac conduction around the doubly ionized oxygen vacancies V o . The last one in high temperature range (above ∼800 K) may be originate from viscous motion of domain wall. Moreover, scaling behavior reveals the dynamic process of electrons is independence of temperature. [ABSTRACT FROM AUTHOR]

We investigate the structural, magnetic, and magnetoelectric properties of DyCr 0.5 Mn 0.5 O 3 . DyCr 0.5 Mn 0.5 O 3 exhibits ferroelectricity at the paramagnetic–antiferromagnetic transition temperature, i.e., T N = 74 K, demonstrating the polarization is driven by magnetic order. Furthermore, the ferroelectric polarization can be substantially influenced by applied magnetic fields indicating a strong magnetoelectric effect in DyCr 0.5 Mn 0.5 O 3 . It is demonstrated that the ferroelectricity in DyCr 0.5 Mn 0.5 O 3 may stem from the spin-phonon coupling of Dy and Mn/Cr ions as evidenced by the temperature dependence of Raman phonon modes. The results manifest that DyCr 0.5 Mn 0.5 O 3 is a potential candidate for magnetoelectric device applications. [ABSTRACT FROM AUTHOR]

The terahertz (THz) conductivities in the metal-insulator transition process of VO 2 thin films on quartz substrates were investigated by using terahertz time-domain spectroscopy. It was found that the THz absorption and conductivity of the thin films are sensitive to the sputtering gas pressure, and the maximum THz amplitude modulation can reach as high as 75.9%. The complex THz conductivity in metallic state of the thin films can be well-fitted by the Drude-Smith model, and the temperature-dependent metallic domain fractions can be extracted by effective medium theory simulation. Based on these results, the metal-insulator transition of the VO 2 thin films can be characterized. The mechanisms of the THz transmission and conductivity were analyzed and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Mg-doped CuAlO2 thin films are prepared by the chemical solution method. The XRD results show that the solid solubility of Mg species on Al sites in CuAlO2 lattice is lower than 2at.%. When less than 2at.% of Mg is added to the CuAlO2 film, the surface roughness of the films was reduced with Mg substitution. Moreover, the c-axis orientation of the films improves because the in-plane fusion between CuAlO2 crystallites is hindered. Optical and electrical measurements show that substituting Al3+ in the films with Mg2+ increases both their transmittance in the visible region and their optical band gaps. As well, their electrical conductivity is enhanced. At 300K, the conductivity of the 1at.% Mg-doped sample is up to 5.2×10−3 S/cm. Thus, Mg-doped CuAlO2 films may have potential applications as transparent conductive oxides. [ABSTRACT FROM AUTHOR]

Abstract: Mn-substituted Bi0.8Ca0.2FeO3 ceramics Bi0.8Ca0.2Fe1−x Mn x O3 (0≤ x ≤0.5) were synthesized by a solid-state reaction method. Powder X-ray diffraction investigations performed at room temperature show that the crystal structure is rhombohedral for x ≤0.1 and orthorhombic for 0.2≤ x ≤0.5. Compared to the undoped Bi0.8Ca0.2FeO3 compound, enhanced magnetization and electric polarization were observed in the samples with x ≤0.1. A further increase in the magnetization with increasing x took place in the samples with 0.2≤ x ≤0.5. All the Mn-substituted samples studied are basically antiferromagnetic accompanied by the appearance of weak ferromagnetism, which is similar to the BiFeO3 compound. The conductivity of the samples with x ≥0.3, measured between 140 and 380K, is of the semiconducting type. [Copyright &y& Elsevier]

Abstract: Single phase CuAlO2 thin films were first successfully prepared on (0001) sapphire substrates by chemical solution deposition method. Additionally, in order to improve the transmittance and conductivity of single phase CuAlO2 thin films, effects of citric acid as additive on phase structure, morphology and optical–electrical property of CuAlO2 thin films were investigated. Appropriate contents of citric acid do not inhibit the formation of single phase CuAlO2 thin films, and are also in favor of improvement of transmittance. Excessive citric acid not only introduces secondary phases, but also deteriorates the quality of the film surface. The mean transmittance in visible region is approximately 50% in the film prepared with 5unit contents of citric acid and its direct and indirect optical band gaps are 3.24eV and 1.8eV, respectively. The films with or without citric acid behave like semiconductors. The resistivity and the activation energy of the film prepared with 5unit contents of citric acid are evaluated as 2.5×102 Ωcm at 290K and 300.5meV, respectively. [Copyright &y& Elsevier]

Abstract: La0.7Sr0.3MnO3 (LSMO) and SrFe12O19 (SFO) samples were synthesized by chemical coprecipitation method. The composites of (1− x)LSMO:xSFO (x is mass%) were prepared using solid-state cosintering. The microstructure, electrical transport, and magnetic properties of the derived composites were systematically investigated. Compared with pure LSMO, the enhancement of low-field magnetoresistance (LFMR) is observed in the composites. The magnetoresistance (MR) value at 300K for the sample with x =0.05 is about 2.9 times larger than that of the pure LSMO. The enhanced MR was attributed to the enhanced spin-dependent intergrain tunneling at the interfaces and grain boundaries due to the enhanced magnetic disorders and antiferromagnetic (AFM) couplings near boundaries between LSMO and SFO grains. [Copyright &y& Elsevier]